Antiviral agents currently in use are of limited effectiveness in treating dermal infections caused by viruses. For example, herpes simplex labialis, commonly referred to as "cold sores" do not respond to the topical treatment with acyclovir (Spruance et al. , Am. J. Med., 73(1A):315-319 (1982); Shaw et al., Br. Med. J. (Clin. Res. Ed.), 291(6487):7-9 (1985); Raborn, et al., Oral Surg. Oral Med. Oral Pathol., 67(6):676-679 (1989); Spruance, et al., Antimicrob. Agents Chemother., 25(5):553-555 (1984); Raborn, et al., J. Can. Dent. Assoc., 55(2):135-137 (1989)). Oral administration of acyclovir for the treatment of cold sores is only partially effective (Spruance et al., J. Infect. Diseases 161:185 (1990)).
The limited effectiveness of antiviral agents such as acyclovir applied topically to cold sores and other dermal viral infections is thought to be a consequence of the limited ability of most of these agents to penetrate the skin (Parry, et al., J. Invest. Dermatol., 98(6):856-863 (1992); Spruance, et al., Antimicrob. Agents Chemother., 25(1):10-15 (1984)). Topical treatments for genital herpes infections are also ineffective for the same reason. Consequently, there is a need for new antiviral agents which can penetrate the skin and which are active against viruses which cause dermal infections.